Process for producing potato chips

ABSTRACT

Fried chips comprising potato solids are made by blanching pieces of raw potatoes containing in excess of 0.2 percent reducing sugar to gel starch contained therein, drying said pieces to a moisture content of about 25 to 60 percent, forming a dough comprising at least about 60 percent by weight of potato solids from said pieces, mixing said dough with yeast and allowing said mixture to ferment for a time sufficient to lower the sugar content below about .[.0.27.]. .Iadd.0.2 .Iaddend.percent by weight of original raw potatoes, forming said dough into chips, drying said chips to a moisture content of from 6-20 percent by weight and frying said chips.

This invention relates to a potato product, and particularly to a deepfat fried potato product, which is of a completely homogeneous nature.This invention also relates to a process for making such products.

There are a great many disadvantages inherent in the methods presentlyemployed in the processing of potatoes in the formation of commercialproducts such as potato chips. Many of these problems relate to the rawpotato from which the product is made.

At the present time, potatoes are commonly cured by storing attemperatures of from 50° - 75° F. for periods up to three months for thepurpose of sugar removal. This requires extensive storage facilities inwhich the temperature and humidity must be carefully controlled.Potatoes so stored tend to sprout to a considerable extent. Thissprouting results in great economic loss due to shrinkage and thenecessity for removing the sprouts prior to processing.

In the production of potato chips according to conventional techniques,after the potatoes have been stored as previously described to lower thesugar level, they are peeled, sliced into chips and washed prior tofrying. Considerable loss of solids occurs during the slicing andwashing operation due to the extremely large surface area of the chips.Commonly, this loss amounts to about 11% of the total solids.

It is well known that natural potatoes vary greatly in theircomposition, such as sugar content, solids content, flavor, etc. Theextent of these variations are influenced by many factors such as thetype of potatoes, the season when harvested, the area where grown, theirculture during the growing season, the length of time they are storedprior to use, etc. These variations result in non-uniformity of productsmade from the potatoes. For example, it is known that the rate ofbrowning of a potato product during processing such as deep fat fryingis influenced by the reducing sugar content of the potato. Therefore,potato chips made from one potato may be much darker in color than thosemade from another potato due to the difference in reducing sugar contentbetween the different potatoes. This correlation between the reducingsugar content of a potato and the extent of browning of chips made fromthe potato imposes a serious limitation on the selection of potatoeswhich may be used in chip manufacture. It has been reported in theliterature that in most instances, acceptably colored chips may be madefrom potatoes of less than 0.2 percent reducing sugars; but that chipsmade from potatoes containing more than 0.25 percent reducing sugargenerally are too dark to be commercially acceptable.

Furthermore, the oil absorption rate of a potato product varies with thesolids content of the potato. Generally, it has been found that forevery 1 percent by weight decrease in solids content of the raw potato,the amount by weight of oil which the potato product is capable ofabsorbing increases by about 11/2 percent. For example, when potatosolids vary from 16 to 17 percent by weight, the amount of oil which thepotato product will absorb will vary from approximately 40 to 381/2percent by weight. This results in potato chips made from differentpotatoes having markedly different oil contents due to variances insolids content of the potatoes.

Moreover, individual potatoes are not of uniform composition. Forexample, each potato contains a layer.[.,.]. a fraction of an inch belowthe surface of the potato, which completely encloses the inner portionof the potato. This layer may be higher in reducing sugar content thanany of the rest of the potato and the portion of the potato which isenclosed by this layer may be of a higher reducing sugar content thanthe portion of the potato lying immediately below the surface. Since therate of browning on frying varies with the reducing sugar content, eachpotato chip may therefore have at least three distinct areas ofdifferent degrees of browning. Moreover, bruises result in localizedareas of high reducing sugar concentrations. Consequently, bruised areaswill generally result in unsightly dark spots on the chips when thechips are fried. Also, the inner portion of a natural potato has a lowersolids content than does the outer portion. Therefore a chip sliced froma natural raw potato will, when fried, have areas of varying oil contentdue to the different rates of oil absorption in the areas of varyingsolids content.

Attempts have been made to produce artificial potato products frompotato flour, mashed potatoes containing a high per cent of gelledstarch, dehydrated potatoes and other farinaceous materials high instarch content. However, none of these techniques .[.have.]. .Iadd.has.Iaddend.achieved a proper balance of true potato flavor and texture inthe resultant product which is necessary in an acceptable commercialproduct.

It is an object of this invention to provide potato products of acompletely homogeneous nature.

It is another object of this invention to eliminate the necessity forstoring raw potatoes for long periods of time prior to processing.

It is a further object of this invention to avoid the high losses ofpotato solids generally associated with potato chip production.

It is another object of this invention to produce high quaulity potatochips from potatoes having a high reducing sugar content.

It is still a further object of this invention to produce from fresh,raw potatoes, which may be of widely divergent compositions andcharacteristics, deep fat fried potato products, such as potato chips,which are of uniform color, texture, flavor, solids content and oilcontent.

It is yet another object of this invention to provide a means forconsistently producing potato chips having the same uniformcharacteristics.

Another object of this invention is to produce a pellet comprisingpotato solids which may be made at or near the area where potatoes aregrown, which may be shipped and/or stored for long periods of time andwhich may be fried in deep fat to produce a potato chip having goodtexture, flavor and color.

These, and other objects, are accomplished by the practice of thisinvention which, briefly, comprises drying potato pieces having amoisture content of at least 70% by weight to a moisture content of fromabout 25 to 60% by weight. These pieces are .[.than.]. .Iadd.then.Iaddend.formed into a dough as by grinding, and the dough is formedinto shaped bodies. The shaped bodies are dried to a moisture content offrom about 6 to 20% weight to form pellets comprising potato solids.These potato pellets may be immediately fried or may be shipped and/orstored for an indefinite period in moisture tight containers.

According to the practice of this invention, potatoes of differentvarieties, sizes and compositions may be used as starting materials.Potatoes generally contain from about 70 to 85% by weight of moisture.The raw potatoes are peeled and blemishes are graded out. The potatoesare then sliced into potatoe pieces and washed by techniques well knownto the art.

The potato pieces should be treated so as to prevent enzymaticdarkening. This is preferably accomplished by blanching the pieces inhot water or with steam for a time sufficient to gel a substantialportion of the starch contained therein -- e.g., at a temperature offrom about 180° to 212° F. for from 1 to 10 minutes. The .[.potator.]..Iadd.potato .Iaddend.pieces are then removed from the blanch water andrinsed with a water spray to cool them and to remove excess free starchfrom the surfaces thereof.

After rinsing, the potato pieces are dried in order to reduce themoisture content thereof to from 25 to 60 percent, and, preferably from35 to 45 percent by weight. The potato pieces may be dried at ambienttemperatures, or, preferably, by heating in an oven at a temperature offrom about 175° to 225° F.

The dried potato pieces are then formed into a dough. This may beaccomplished by grinding them in a food grinder which is fitted with agrinding plate having hole sizes one-fourth inch or less in diameter.

If the raw potatoes which are used in the process of this invention havea reducing sugar content in excess of 0.2 percent by weight, it ispreferred to treat the potatoes to lower the sugar content. This may beaccomplished by adding from about 0.1 to 1.0 percent by weight of yeast,based on the total solids content, to the dried potato pieces beforethey are ground into a dough. The yeast may be added to the potatopieces in the form of an aqueous slurry. It is preferred that the potatopieces to which the yeast is added have a moisture content within therange of 50 to 60 percent by weight. The yeast-treated pieces arepreferably formed into a dough at a temperature of from about 80° to115° F. The dough is then allowed to ferment at a temperature of from75° to 100° F. for from 1 to 4 hours. By controlling the reducing sugarcontent of the dough, the extent of browning of the final product mayalso be controlled. Since het browning does not occur unless reducingsugars are present, browning may be controlled by removal of a portionof this constituent. If the reducing sugar content of the raw potatoesis below about .[.1.2.]. .Iadd.0.2 .Iaddend.percent, yeast treatment isnot necessary.

Before the potato dough is formed into shaped bodies, it may be admixedwith other starch containing materials such as rice flour, tapiocaflour, potato starch, potato flour, wheat flour etc. It is preferredthat not more than about 40 percent by weight of the total solids in thedough be other starch containing material. If other starch containingmaterial is mixed with the potato dough, the moisture content of theresultant dough should still be between 25 to 60 percent by weight, andpreferably between 35 to 45 percent by weight, before it is formed intoshaped bodies.

In forming the dough into shaped bodies, it is preferred to extrude thedough into a ribbon, to air dry the ribbon in order to case harden it sothat the surfaces thereof are not adherent, and then to cut the ribboninto shaped bodies. A suitable extrusion apparatus is one which iscapable of generating high pressures and elevated temperatures and whichexerts a high degree of shear force on the dough. It is preferred toemploy an extruder fitted with a tapered auger which will raise thetemperature of the dough to within the range of 175° to 215° F. when itemerges from the extrusion orifice.

The extruded ribbon, which preferably has a thickness of between about0.015 and 0.045 inch may be cut into shaped bodies by conventional meanssuch as with a die. While the process is being run in a continuousmanner, it is preferred to recycle any excess dough from the ribbon tothe extruder to be mixed with fresh dough.

The shaped bodies are then dried to a moisture content of from 6 to 20percent, and preferably 8 to 16 percent by weight. This drying may beaccomplished by placing them in a hot air oven which is heated to atemperature of from 120° to 140° F. for from 40 to 80 minutes.

The resultant dried potato pellets may be fried immediately or they maybe shipped in moisture tight containers and/or stored for an indefiniteperiod of time. Thus, the pellets may be made at or near the area wherethe potatoes are grown and then shipped to other parts of the countryfor frying. This results in considerable savings in transportation costsas compared to shipping raw potatoes since the pellets contain much lessmoisture than do raw potatoes.

Any conventional apparatus which is ordinarily used for deep fat fryingmay be employed to cook the potato products of this invention. Thefrying may be accomplished by means of a batch operation, in which abatch of the pellets are charged directly into the cooker, agitated andthen removed; or by means of a continuous frying process, in which thepellets are fed into one end of a cooker and are continuously removedfrom the other end.

The type and temperature of fat or oil used to cook the chips are thoseconventionally used in deep fat frying potato chips. There may be used,for example, cottonseed oil, peanut oil, corn oil, soybean oil, coconutoil or mixtures thereof. The temperature in the cooker generally variesbetween about 345° and 395° F. Frying time may vary between 12 and 60seconds.

During the frying operation, the pellets expand considerably, losemoisture and take up oil. The fried chips are removed from the fryer,excess oil is shaken off and the chips are then salted and packaged.

Chips made in accordance with the practice of this invention have amoisture content below about 3.5 percent by weight and an oil content offrom about 30 to 36 percent by weight. The products are characterized byuniformity of color, flavor, texture, oil content, size, etc., bothwithin each individual chip and between all of the chips. They are crispand have an elegant flavor. Moreover, they are sufficiently rigid towithstand breakage during packaging and shipping and during use withdips.

The following examples illustrate the best modes contemplated forcarrying out this invention. In these examples, all percentages are byweight unless otherwise specified.

EXAMPLE 1

Raw potatoes (100 lbs.) having a moisture content of approximately 80%and a reducing sugar content of less than 0.2% are peeled, trimmed tograde out blemishes and washed leaving about 94 lbs. of potatoes. Thepotatoes are then sliced into French cut shapes about 3.8 inch inthickness. These slices are blanched by contacting them with steam in achamber maintained at atmospheric pressure for 21/3 minutes. The steamin introduced to the chamber at a pressure of 15 p.s.i. and thetemperature in the chamber is thereby raised to 198° F. The blanchedpotato slices are removed from the chamber, excess free starch is rinsedfrom the surfaces of the pieces and the pieces are cooled by a waterspray. Excess water is drained from the potato pieces and they are thenpassed through a hot air drying oven. The oven is operated at atemperature of about 200° F. and an air velocity of about 200 feet perminute. The dried potato pieces have a moisture content of about 40% andweigh about 30 lbs. The dried potato pieces are ground in a meat grinderfitted with a grinding plate having orifices 1/16 inch in diameter toproduce a uniformly mixed potato dough. This dough is fed into anextruder fitted with a tapered auger. In the extruder, the potato doughis subjected to a high degree of shear force. The dough emerges from theextruder at a temperature of about 200° F. in a strip or ribbon 10inches wide and about 0.020 to 0.025 inch in thickness. The extrudedribbon, which is in a uniform, amorphous form, is then cooled and thesurface is air dried to case harden and render it non-sticky. The ribbonis then cut by means of a die into pellets which are dried to a moisturecontent of 12% by passing them through a hot air dryer at a temperatureof 130° F. for 50 minutes. The pellets are then fried by submerging themfor about 13 to 15 seconds in frying oil heated to a temperature ofabout 370° F. During frying, the pellets expand and form chips having acrisp friable texture, a golden color and good potato chip flavor. Thefried chips contain about 35% oil. The chips are then salted andpackaged. About 26 to 28 lbs. of fried chips are produced from theoriginal 100 lbs. of raw potatoes.

EXAMPLE 2

Raw potatoes (100 lbs.) having a moisture content of about 80% and areducing sugar content of about 1.0% are peeled, trimmed and sliced asdescribed in Example 1. They are then blanched by immersion in boilingwater for 11/2 minutes and washed to remove free starch. The potatopieces are then dried to a moisture content of about 52.5% and a weightof about 38 lbs. A yeast slurry is then blended with the dried potatopieces in an amount sufficient to give 0.3% of yeast based on the totalsolids content of the mixture. This requires 0.054 lbs. of active drygranulated yeast for the approximately 38 lbs. of dried potatoes. Theyeast slurry is prepared by suspending the 0.054 lb. of active drygranulated yeast in about 6.3 lbs. of water. The potato pieces havingthe yeast coated on the surfaces thereof are ground in a meat grinderfitted with a grinding plate having orifices 1/16 inch in diameter andhaving a cooling jacket to maintain a dough temperature of 96° F. Theresultant potato dough is allowed to ferment for 21/2 hours in a highhumidity environment at a temperature of 85° F. After fermentation, thedough is extruded into pieces 1/4 inch in diameter and 1 inch long.These pieces are dried to a moisture content of 40% and are fed into anextruder, extruded into a ribbon, cut into pellets, dried and the driedpellets fried as described in Example 1. The resultant chips have goodcolor and flavor. By contrast, chips made by conventional techniquesfrom potatoes having the same sugar content as those used in thisexample have a very dark, burned appearance.

EXAMPLE 3

Example 1 is repeated except that before the 30 lbs. of dried potatopieces having a moisture content of about 40% are ground in a grinder,they are blended with 5 lbs. of rice flour (containing a moisturecontent of 10%) and 2.5 lbs. of water. This results in a doughcomprising a solids content of 20% rice solids and 80% potato solids.The yield of dried pellets having a moisture content of 12% is about25.5 lbs. and the yield of fried chips is between 32 to 36 lbs.

EXAMPLE 4

A fermented potato dough is prepared as described in Example 2. Afterfermentation, the potato dough is blended with 16 lbs. of rice flourhaving a moisture content of 10%. The resultant dough contains potato30% rice solids and 70% potato solids and has a moisture content ofabout 40%. This dough is then extruded into a ribbon, cut into pellets,dried, and the dried pellets fried as described in Example 1. The yieldof dried pellets is about 37 lbs. and the yield of fried chips is about49 lbs.

Although the invention has been described in considerable detail withreference to certain preferred embodiments thereof, it will beunderstood that variations and modifications can be made withoutdeparting from the spirit and scope of the invention as describedhereinabove and as defined in the claims which follow.

We claim:
 1. A process for producing potato chips which comprises:1.blanching pieces of raw potato containing in excess of 0.2 percent byweight of reducing sugar which are subject to enzymatic darkening andwhich have a moisture content of at least 70 percent by weight in wateror steam at a temperature of from about 180° to 212° F. for a timesufficient to gelatinize starch contained therein and to preventenzymatic darkening;
 2. drying said potato pieces to a moisture contentof from 25-60 percent by weight;
 2. .Badd..[.3..]..Baddend. forming adough containing yeast from said pieces, the total solids in said doughcomprising at least 60 percent by weight of potato solids, and allowingsaid dough to ferment for a time sufficient to lower the reducing sugarcontent to below about 0.2 percent by weight of original raw potatoes;4. forming said dough into chips;
 5. drying said chips to a moisturecontent of from 6-20 percent by weight; and
 6. frying said chips.
 2. Theprocess of claim 1 wherein said dough contains from about 0.1 to 1.0percent by weight of yeast based on the total solids content.
 3. Theprocess of claim 2 wherein up to 40 percent by weight of the potatosolids content of said dough is replaced with another starch containingmaterial.
 4. The process of claim 3 wherein said other starch containingmaterial is rice flour.
 5. The process of claim 2 wherein said dough isextruded into a ribbon, the surfaces of said ribbon are air dried andshaped bodies are cut from said ribbon.
 6. The process of claim 2wherein said shaped bodies are dried to a moisture content of from 8 to16 percent by weight.
 7. A process for the production of a fried potatoproduct from potatoes containing in excess of 0.2 percent by weight ofreducing sugars which comprises forming a .Iadd.potato .Iaddend.doughcomprising said potatoes .Iadd., water .Iaddend.and yeast, said yeastbeing present in an amount sufficient to ferment said reducing sugars,allowing said dough to ferment for a time sufficient to lower thereducing sugar content .Iadd.to .Iaddend.below about 0.2 percent byweight .[.of.]. .Iadd.based on .Iaddend.said potatoes, forming the doughinto shaped bodies and frying said shaped bodies.
 8. A process forproducing potato chips which comprises:1. blanching pieces of rawpotatoes containing in excess of 0.2 percent by weight of reducing sugarwhich are subject to enzymatic darkening and which have a moisturecontent of at least 70 percent by weight in water or steam at atemperature of from about 180° F. to 212° F. for a time sufficient togelatinize starch conained therein and to prevent enzymatic darkening;2. drying said potato pieces to a moisture content of from 25-60 percentby weight;
 3. forming a dough from said potato pieces, the total solidsin said dough comprising at least about 60 percent by weight of potatosolids;4. mixing said dough with yeast and allowing the mixture toferment for a time sufficent to lower the sugar content below about 0.2percent by weight of original raw potatoes;
 5. raising the temperatureof said dough to within the range of 175° to 215° F. and forming saiddough into chips;
 6. drying said chips to a moisture content of from6-20 percent by weight; and
 7. frying said chips in deep fat.
 9. Theprocess of claim 8 wherein from about 0.1 to 1.0 percent by weight ofyeast based on the total solids content is added to aid dough. .Iadd.10. A process of claim 7 in which the dough is formed into shaped bodieswhich are fried to provide potato chips..Iaddend..Iadd.
 11. A process ofclaim 10 in which the total solids in said dough comprises at leastabout 60 percent by weight of potato solids..Iaddend. .Iadd.
 12. Aprocess for the production of a potato product from potatoes containingin excess of 0.2 percent by weight of reducing sugars which comprisesfermenting a potato dough comprising potato solids from said potatoes,water and yeast in an amount sufficient to ferment said reducing sugars,said fermenting being continued for a time sufficient to lower thereducing sugar content to below about 0.2 percent by weight based onsaid potatoes, and forming the dough into shaped bodies forfrying..Iaddend..Iadd.
 13. A process of claim 12 in which the dough isformed into shaped bodies which upon frying are potatochips..Iaddend..Iadd.
 14. A process of claim 13 in which the totalsolids insaid dough comprises at least about 60 percent by weight ofpotato solids..Iaddend..Iadd.
 15. A process for the production of afried potato product from potatoes containing in excess of 0.2 percentby weight of reducing sugars which comprises fermenting a potato doughcomprising potato solids from aid potatoes, water and yeast in an amountsufficient to ferment said reducing sugars, said fermenting beingcontinued for a time sufficient to lower the reducing sugar content tobelow about 0.2 percent by weight based on said potatoes, forming thedough into shaped bodies and frying said shaped bodies..Iaddend..Iadd.16. A process of claim 15 in which the dough is formed into shapedbodies which are fried to provide potato chips..Iaddend..Iadd.
 17. Aprocess of claim 16 in which the total solids in said dough comprises atleast about 60 percent by weight of potato solids..Iaddend..Iadd.
 18. Aprocess for the production of a potato product from potatoes containingin excess of 0.2 percent by weight of reducing sugars which comprisesforming a potato dough comprising potato solids from said potatoes,water and yeast in an amount sufficient to ferment said reducing sugars,fermenting said dough for a time sufficient to lower the reducing sugarcontent to below about 0.2 percent by weight based on said potatoes, andforming the dough into shaped bodies for frying..Iaddend..Iadd.
 19. Aprocess of claim 18 in which the dough is formed into shaped bodieswhich upon frying are potato chips..Iaddend..Iadd.
 20. A process ofclaim 19 in which the total solids in said dough comprises at lest about60 percent by weight of potato solids..Iaddend.